1. Technical Field
The present invention relates to a hydrogen generating apparatus and a fuel cell power generation system.
2. Description of the Related Art
A fuel cell is an apparatus that converts the chemical energies of fuel (hydrogen, LNG, LPG, methanol, etc.) and air directly into electricity and heat, by means of electrochemical reactions. In contrast to conventional power generation techniques, which employ the processes of burning fuel, generating vapor, driving turbines, and driving power generators, the utilization of fuel cells does not entail combustion processes or driving apparatus. As such, the fuel cell is the result of new technology for generating power that offers high efficiency and few environmental problems.
FIG. 1 is a diagram illustrating the operating principle of a fuel cell.
Referring to FIG. 1, a fuel cell 100 may include a fuel electrode 110 as an anode and an air electrode 130 as a cathode. The fuel electrode 110 receives molecular hydrogen (H2), which is dissociated into hydrogen ions (H+) and electrons (e−). The hydrogen ions move past a moisture absorption layer 126 towards the air electrode 130. This moisture absorption layer 120 corresponds to an electrolyte layer. The electrons move through an external circuit 140 to generate an electric current. The hydrogen ions and the electrons combine with the oxygen in the air at the air electrode 130 to generate water. The following Reaction Scheme 1 represents the chemical reactions described above.

In short, the fuel cell can function as a battery, as the electrons dissociated from the fuel electrode 110 generate a current that passes through the external circuit. Such a fuel cell 100 is a relatively pollution-free power source, because it does not produce any polluting emissions such as SOx, NOx, etc., and produces only little amounts of carbon dioxide. The fuel cell may also offer several other advantages, such as low noise and little vibration, etc.
In order for the fuel cell 100 to generate electrons at the fuel electrode 110, a hydrogen generating apparatus may be needed, which modifies a regular fuel containing hydrogen atoms into a gas having a high hydrogen content, as required by the fuel cell 100.
Examples of fuel cells being researched for application to portable electronic devices include the polymer electrolyte membrane fuel cell (PEMFC), which uses hydrogen as fuel, and the direct liquid fuel cell, such as the direct methanol fuel cell (DMFC), which uses liquid fuel directly. The PEMFC provides a high output density, but requires a separate apparatus for supplying hydrogen. Using a hydrogen storage tank, etc., for supplying the hydrogen can result in a large volume and can require special care in handling and keeping.
FIG. 2 is a cross-sectional view schematically illustrating a conventional hydrogen generating apparatus, and FIG. 3 is a diagram illustrating a mode of connecting electrodes in a conventional hydrogen generating apparatus. As illustrated, an anode 220 made of magnesium and a cathode 230 made of stainless steel may be dipped in an aqueous electrolyte solution 215 inside an electrolyte bath 210.
The basic principle of the hydrogen generating apparatus 200 is that electrons are generated at the magnesium electrode 220, which has a greater tendency to ionize than the stainless steel electrode 230, and the generated electrons travel to the stainless steel 230 electrode. The electrons can then react with the aqueous electrolyte solution 215 to generate hydrogen.
Here, positioning the magnesium and stainless steel electrodes in alternation, as illustrated in FIG. 3, can increase the amount of hydrogen generated. However, in a hydrogen generating apparatus structured as such, an increase in the number of electrodes may lead to an increase in volume occupied by the electrodes, and thus may not be applicable in compact and low-thickness electronic devices.
In order for the fuel cell to suitably accommodate the demands in current portable electronic devices (e.g. cell phones, laptops, etc.) for high-capacity power supply apparatus, the fuel cell needs to have a small volume while providing high performance.
The fuel cell may employ a method of generating hydrogen after reforming fuel, such as methanol or formic acid, etc., approved by the ICAO (International Civil Aviation Organization) for boarding on airplanes, or may employ a method of using methanol, ethanol, or formic acid, etc., directly as the fuel.
However, the former case may require a high reforming temperature, a complicated system, and high driving power, and is likely to have impurities (e.g. CO2, CO, etc.) included, besides pure hydrogen. On the other hand, the latter may entail the problem of very low power density, due to the low rate of a chemical reaction at the anode and the cross-over of hydrocarbons through the moisture absorption layer.